Digital mammography is one of the key research areas for improvements in the detection of breast cancer through large scale screening programs. Primary digital acquisition appears to have theoretical advantages for generation of high quality images compared to film-screen receptors, including potentially superior latitude and dose efficiency. Digital radiography systems based on CCDs with X-ray-to-light convertors and demagnifying optics are starting to replace X-ray film for some small- area mammography procedures. However, technological considerations limit the maximum area that this type of system can practically image to less than that required for general screening purposes. These optical-based sensors also suffer from significantly X-ray image quality problems due to light spreading in the X-ray convertor. We propose to develop a large-area X-ray imaging sensor based on a CMOS pixel array that overcomes these limitations. The incoming radiation is directly imaged using an X-ray sensitive photoconductor, lead iodide (PbI2) with nearly 100% efficiency. This system will use standard CMOS silicon technology that has the ability to be scaled up to large areas (18 x 24 cm2) at relatively low cost without sacrificing image quality. This low-cost, compact system may be fabricated into standard size formats with dramatically improve image quality to serve as direct replacements of X- ray film mammography cassettes for screening mammography PROPOSED COMMERCIAL APPLICATION: The market for mammography screening equipment is in the billions of dollars. A low-cost, large-area format X-ray imager with significantly higher image quality than current systems provide will find widespread acceptance in many medical and industrial settings.